SEVERN TOWNSHIP, ONT. -- Ken MacDonald spends a lot of time looking way up into the trees, watching birds.

But his binoculars captured something unexpected at a heron nesting ground in Severn Township on Tuesday: a black bear in a treetop heron's nest in search of lunch.

"This must have been one determined bear or one hungry bear because he climbed up four or five storeys up to the top of this tree and got in the nest," MacDonald says.

MacDonald says that in spring, a heronry, or area where herons nest, is typically noisy with bird chicks pleading for food. But with the bear nearby, there was only eerie quiet.

MacDonald watched the bear in amazement for an hour. Photos he's shared of the encounter online have picked up international attention.

"It's great to see a bear, especially one that doesn't run away right away. So we were quite excited about seeing it. Of course, you feel a little bad for the herons," MacDonald says.

Mike McIntosh, the founder and president of the Bear With Us Centre for Bears, who has been working with the animals for nearly 30 years, is impressed.

"It wouldn't be really common because it would take a very hungry bear to climb that high on a very spindly old tree. And then it has to be a small bear, a young bear that's not fully grown to be able to do that."

McIntosh says it was likely the bear's strong sense of smell that propelled the bear upward in search of food.

"It probably found out that (heron) eggs taste good and could smell the eggs way up on the top of those trees," McIntosh says.

He explains that in the spring, bears are typically living off some leftover body fat from the colder months, adding in some plants. But as the temperature rises, their diets shift.

"The grass is no longer edible, and neither are the leaves. So they get pretty hungry because they're just walking around with nothing to eat. And then they'll start looking for other things-grubs and insects. In this case, blue heron eggs."

McIntosh says bears will have a new food supply when berries ripen in about a month. Until then, he advises that homeowners put their bird feeders and food waste out of reach to help bears and humans co-exist peacefully.